1. Technical Field
The present invention relates to stacks for the removal of combustion products and more particularly, to methods and apparatus for removing liquid from liquid and gas mixtures in such stacks. Still more particularly, this invention relates to the removal of liquids from gasses entrained in stacks of wet scrubbed coal fired electrical generating plants.
2. Background Information
The prior art discloses various apparatus and methods for separating entrained liquids from a gas stream in stacks and other locations.
U.S. Pat. No. 3,348,364 to Henby, for example, discloses a wet type, updraft gas scrubber comprising a vertical cylindrical housing with inlet means adjacent the lower end and outlet means adjacent the upper end, a filter bed extending transversely across the housing intermediate the inlet and outlet comprising a plurality of spherical filter elements, liquid spray means for introducing fine liquid droplets into the gas flowing upwardly into the filter bed to wet and collect contaminants in the gas, separator means intermediate said filter bed and the outlet for removing and collecting any liquid or mist remaining in the gas flowing upwardly from said filter bed, said separator means including a pair of rings defining an annular flow path substantially smaller in cross section than the housing for accelerating the gas flow therethrough and a plurality of adjustable deflecting vanes mounted between said rings in said flow path for directing the high velocity, upwardly flowing gas outwardly with a horizontal component against the housing wall, an annular liquid collecting trough between the outer ring and said housing wall for collecting liquid centrifuged outwardly against the wall, and drain means for said trough directing the collected liquid onto said filter bed.
U.S. Pat. No. 3,543,485 to Hardison discloses a vessel wall cooperating with a circular array of moisture separators which have a vertical riser tube, centrally disposed hubs, a vertical baffle disposed between the hub and the riser tube, turning vanes and an outer volute partial skirt or wall to compress the steam-water mixture against the volute and vessel wall and utilize the downwardly spiraling flow of liquid film formed on the volute and vessel wall to effectively separate the entrained water from the steam and prevent re-entrainment thereof.
U.S. Pat. No. 4,322,233 to Sisk discloses vertically aligned centrifugal particle separator wherein a multiplicity of static vanes extend upward from and are circumferentially fixed around a static spinner. The spinner has a hub and blades and is axially mounted over a particle laden gas inlet. A gas stream rising from the gas inlet is forced into an ascending spiral by the spinner blades. Relatively dense particles entrained in the gas stream are thrown centrifugally outward and are either passed between static vanes or strike static vanes, and in either case are deflected into a particle receiving section, which is the space bounded by the outer surfaces of the gas inlet and the static vanes and the inner surface of the centrifugal particle separator.
U.S. Pat. No. 5,201,919 to John, et al. discloses a gas scrubbing device having inlet and outlet ports that allows a gas stream to enter the scrubber from the bottom and exit through the top. The gas direction is reversed several times, fed through a venturi to accelerate the gas flow, and passed over two sumps containing scrubbing liquid. The combination of the high speed gas flow, gas flow reversal, and scrubbing liquid removes most particulates from the gas. The gas flows upward through a mist of scrubbing liquid created by a spray nozzle, and as the gas flows beyond the mist it flows through a series of serpentine vanes which cause the gas to change direction flow removing additional liquid droplets from the gas, through a reducing element, and out through the outlet port.
A need still exists, however, to improve the efficiency of liquid removal from gas entrained in stacks.
A need also exists for an improved means for preventing liquid droplets from falling from stack planes in areas adjacent the stack.
An object of the present invention is to provide an easy, inexpensive and efficient method and apparatus for separating liquid entrained in a gas stream in particularly of an existing stack, or new stack.
Another object of the present invention is to provide an improved method and apparatus for preventing liquid droplets from falling from stack planes in areas adjacent the stack.
The above objects are accomplished by the present invention which is a method and apparatus for imparting a swirling velocity component to a gas flow in a stack and then collecting entrained liquid droplets at the top of the stack. The apparatus used to impart this swirling motion comprises a plurality of parallel vertical vanes positioned in front of ducts at the base of the stack. As gas flows inwardly through the ducts to the stack, it encounters the vanes which are positioned at a selected preferred angle to impart the desired swirl.